This project examines the structure and function of neural systems that are hypothesized to contribute to age-related declines in speech recognition. Large age-related differences in speech recognition are observed in complex and demanding listening environments for reasons that are unclear. Aging brains undergo extraordinary changes and there is little understanding of how these changes limit or preserve cognitive abilities. We propose to track the aging of two neural systems that play central roles in hypotheses for declines in speech recognition. Aim 2.1 tests the hypothesis that age-related anatomical declines in brain regions that support speech recognition lead to increased reliance on attention-related frontal cortex for word recognition in normal hearing adults. Aim 2.2 tests the hypothesis that older adults with normal hearing exhibit speech recognition declines when additive anatomical declines within speech-related and attention-related systems limit the ability to attend to degraded speech. Aim 2.3 tests the hypothesis that the most common form of age-related hearing loss, metabolic presbyacusis, leads to compensatory changes within speech-related and attention-related systems. This project uses brain activation experiments to define speech-responsive brain regions where anatomical declines may explain the connection between the aging brain and speech recognition difficulties. This project will provide an understanding of the age-related neurobiological changes that people with normal hearing and with hearing loss experience and thereby provide a foundation for improving the speech recognition of older adults through the development of intervention strategies that are based on the peripheral and central nervous system changes that occur with age.